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Valdetaro LB, Jensen MB, Muren LP, Skyt PS, Petersen JBB, Balling P. Technical note: Temporal and thermal stability of optical response for silicone-based 3D radiochromic dosimeters. Med Phys 2022; 50:2560-2564. [PMID: 36585852 DOI: 10.1002/mp.16193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 11/28/2022] [Accepted: 12/13/2022] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Radiochromic silicone-based dosimeters are flexible 3D dosimeters, which at appropriate concentration of leucomalachite green (LMG) and curing agent are dose-rate independent for clinical photon beams. However, their dose response is based on chemical processes that can be influenced by temporal and thermal conditions, impacting measurement stability. PURPOSE The aim of this study was to investigate the temporal stability of the dose response of radiochromic dosimeters for different curing times and post-irradiation storage temperatures. METHODS Six cylindrical dosimeters (5 cm diameter, 5 cm length) were produced in a single batch and separated into two groups that were irradiated 72 and 118 h after production. The same photon plan, consisting of two 10 × 1.6 cm2 opposing fields, was delivered to all dosimeters. After irradiation, the dosimeters were separated into three groups, stored at 5°C, 15°C, and 20°C, and read out for five consecutive days. RESULTS Storage temperature influenced the measurement stability, and changes in the optical response with time differed between irradiated and non-irradiated parts of the dosimeters. The relative change between signal and background was greater than 10% for all measurements performed 24 h or more after irradiation, except for dosimeters stored at 5°C, which changed by 2%-5% after 24 h. The dosimeter temporal stability was not influenced by curing time. CONCLUSIONS For room temperature storage (15°C and 20°C), readout should take place as soon as possible after irradiation since the background color increased rapidly for both curing times (72 and 118 h), whereas the dosimeters are stored at 5°C, readout can be performed up to 24 h after.
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Affiliation(s)
- Lia Barbosa Valdetaro
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Morten Bjørn Jensen
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark
| | - Ludvig Paul Muren
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | | | - Jørgen Breede Baltzer Petersen
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark
| | - Peter Balling
- Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark.,Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, Denmark
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De Deene Y. Radiation Dosimetry by Use of Radiosensitive Hydrogels and Polymers: Mechanisms, State-of-the-Art and Perspective from 3D to 4D. Gels 2022; 8:599. [PMID: 36135311 PMCID: PMC9498652 DOI: 10.3390/gels8090599] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 09/07/2022] [Accepted: 09/10/2022] [Indexed: 12/22/2022] Open
Abstract
Gel dosimetry was developed in the 1990s in response to a growing need for methods to validate the radiation dose distribution delivered to cancer patients receiving high-precision radiotherapy. Three different classes of gel dosimeters were developed and extensively studied. The first class of gel dosimeters is the Fricke gel dosimeters, which consist of a hydrogel with dissolved ferrous ions that oxidize upon exposure to ionizing radiation. The oxidation results in a change in the nuclear magnetic resonance (NMR) relaxation, which makes it possible to read out Fricke gel dosimeters by use of quantitative magnetic resonance imaging (MRI). The radiation-induced oxidation in Fricke gel dosimeters can also be visualized by adding an indicator such as xylenol orange. The second class of gel dosimeters is the radiochromic gel dosimeters, which also exhibit a color change upon irradiation but do not use a metal ion. These radiochromic gel dosimeters do not demonstrate a significant radiation-induced change in NMR properties. The third class is the polymer gel dosimeters, which contain vinyl monomers that polymerize upon irradiation. Polymer gel dosimeters are predominantly read out by quantitative MRI or X-ray CT. The accuracy of the dosimeters depends on both the physico-chemical properties of the gel dosimeters and on the readout technique. Many different gel formulations have been proposed and discussed in the scientific literature in the last three decades, and scanning methods have been optimized to achieve an acceptable accuracy for clinical dosimetry. More recently, with the introduction of the MR-Linac, which combines an MRI-scanner and a clinical linear accelerator in one, it was shown possible to acquire dose maps during radiation, but new challenges arise.
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Affiliation(s)
- Yves De Deene
- Liverpool & Macarthur Cancer Therapy Centres, Liverpool, NSW 1871, Australia; or
- Ingham Institute, Liverpool, NSW 2170, Australia
- School of Science, Western Sydney University, Penrith, NSW 2751, Australia
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3
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Gagliardi FM, Franich RD, Geso M. Dose response and stability of water equivalent PRESAGE® dosimeters for synchrotron radiation therapy dosimetry. ACTA ACUST UNITED AC 2018; 63:235027. [DOI: 10.1088/1361-6560/aaf1f5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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4
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Costa F, Doran SJ, Hanson IM, Nill S, Billas I, Shipley D, Duane S, Adamovics J, Oelfke U. Investigating the effect of a magnetic field on dose distributions at phantom-air interfaces using PRESAGE ® 3D dosimeter and Monte Carlo simulations. Phys Med Biol 2018; 63:05NT01. [PMID: 29393066 PMCID: PMC5964337 DOI: 10.1088/1361-6560/aaaca2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 01/22/2018] [Accepted: 02/02/2018] [Indexed: 11/23/2022]
Abstract
Dosimetric quality assurance (QA) of the new Elekta Unity (MR-linac) will differ from the QA performed of a conventional linac due to the constant magnetic field, which creates an electron return effect (ERE). In this work we aim to validate PRESAGE® dosimetry in a transverse magnetic field, and assess its use to validate the research version of the Monaco TPS of the MR-linac. Cylindrical samples of PRESAGE® 3D dosimeter separated by an air gap were irradiated with a cobalt-60 unit, while placed between the poles of an electromagnet at 0.5 T and 1.5 T. This set-up was simulated in EGSnrc/Cavity Monte Carlo (MC) code and relative dose distributions were compared with measurements using 1D and 2D gamma criteria of 3% and 1.5 mm. The irradiation conditions were adapted for the MR-linac and compared with Monaco TPS simulations. Measured and EGSnrc/Cavity simulated profiles showed good agreement with a gamma passing rate of 99.9% for 0.5 T and 99.8% for 1.5 T. Measurements on the MR-linac also compared well with Monaco TPS simulations, with a gamma passing rate of 98.4% at 1.5 T. Results demonstrated that PRESAGE® can accurately measure dose and detect the ERE, encouraging its use as a QA tool to validate the Monaco TPS of the MR-linac for clinically relevant dose distributions at tissue-air boundaries.
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Affiliation(s)
- Filipa Costa
- Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS
Foundation Trust, London SM2 5NG, United
Kingdom
| | - Simon J Doran
- CRUK Cancer Imaging Centre, The Institute of Cancer Research, London SM2
5NG, United Kingdom
| | - Ian M Hanson
- Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS
Foundation Trust, London SM2 5NG, United
Kingdom
| | - Simeon Nill
- Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS
Foundation Trust, London SM2 5NG, United
Kingdom
| | - Ilias Billas
- Metrology for Medical Physics, National Physical Laboratory, Hampton Road,
Teddington TW11 0LW, United Kingdom
| | - David Shipley
- Metrology for Medical Physics, National Physical Laboratory, Hampton Road,
Teddington TW11 0LW, United Kingdom
| | - Simon Duane
- Metrology for Medical Physics, National Physical Laboratory, Hampton Road,
Teddington TW11 0LW, United Kingdom
| | - John Adamovics
- Department of Chemistry and Biology, Rider University, Lawrenceville, NJ 08648,
United States of America
| | - Uwe Oelfke
- Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS
Foundation Trust, London SM2 5NG, United
Kingdom
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Pappas EP, Zoros E, Moutsatsos A, Peppa V, Zourari K, Karaiskos P, Papagiannis P. On the experimental validation of model-based dose calculation algorithms for192Ir HDR brachytherapy treatment planning. Phys Med Biol 2017; 62:4160-4182. [DOI: 10.1088/1361-6560/aa6a01] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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6
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McErlean CM, Bräuer-Krisch E, Adamovics J, Doran SJ. Assessment of optical CT as a future QA tool for synchrotron x-ray microbeam therapy. Phys Med Biol 2016; 61:320-37. [PMID: 26657052 DOI: 10.1088/0031-9155/61/1/320] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Synchrotron microbeam radiation therapy (MRT) is an advanced form of radiotherapy for which it is extremely difficult to provide adequate quality assurance. This may delay or limit its clinical uptake, particularly in the paediatric patient populations for whom it could be especially suitable. This study investigates the extent to which new developments in 3D dosimetry using optical computed tomography (CT) can visualise MRT dose distributions, and assesses what further developments are necessary before fully quantitative 3D measurements can be achieved. Two experiments are reported. In the first cylindrical samples of the radiochromic polymer PRESAGE(®) were irradiated with different complex MRT geometries including multiport treatments of collimated 'pencil' beams, interlaced microplanar arrays and a multiport treatment using an anthropomorphic head phantom. Samples were scanned using transmission optical CT. In the second experiment, optical CT measurements of the biologically important peak-to-valley dose ratio (PVDR) were compared with expected values from Monte Carlo simulations. The depth-of-field (DOF) of the optical CT system was characterised using a knife-edge method and the possibility of spatial resolution improvement through deconvolution of a measured point spread function (PSF) was investigated. 3D datasets from the first experiment revealed excellent visualisation of the 50 μm beams and various discrepancies from the planned delivery dose were found. The optical CT PVDR measurements were found to be consistently 30% of the expected Monte Carlo values and deconvolution of the microbeam profiles was found to lead to increased noise. The reason for the underestimation of the PVDR by optical CT was attributed to lack of spatial resolution, supported by the results of the DOF characterisation. Solutions are suggested for the outstanding challenges and the data are shown already to be useful in identifying potential treatment anomalies.
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Affiliation(s)
- Ciara M McErlean
- CRUK Cancer Imaging Centre, Institute of Cancer Research, London, SM2 5NG, UK
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Bräuer-Krisch E, Adam JF, Alagoz E, Bartzsch S, Crosbie J, DeWagter C, Dipuglia A, Donzelli M, Doran S, Fournier P, Kalef-Ezra J, Kock A, Lerch M, McErlean C, Oelfke U, Olko P, Petasecca M, Povoli M, Rosenfeld A, Siegbahn EA, Sporea D, Stugu B. Medical physics aspects of the synchrotron radiation therapies: Microbeam radiation therapy (MRT) and synchrotron stereotactic radiotherapy (SSRT). Phys Med 2015; 31:568-83. [PMID: 26043881 DOI: 10.1016/j.ejmp.2015.04.016] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 04/27/2015] [Accepted: 04/28/2015] [Indexed: 11/19/2022] Open
Abstract
Stereotactic Synchrotron Radiotherapy (SSRT) and Microbeam Radiation Therapy (MRT) are both novel approaches to treat brain tumor and potentially other tumors using synchrotron radiation. Although the techniques differ by their principles, SSRT and MRT share certain common aspects with the possibility of combining their advantages in the future. For MRT, the technique uses highly collimated, quasi-parallel arrays of X-ray microbeams between 50 and 600 keV. Important features of highly brilliant Synchrotron sources are a very small beam divergence and an extremely high dose rate. The minimal beam divergence allows the insertion of so called Multi Slit Collimators (MSC) to produce spatially fractionated beams of typically ∼25-75 micron-wide microplanar beams separated by wider (100-400 microns center-to-center(ctc)) spaces with a very sharp penumbra. Peak entrance doses of several hundreds of Gy are extremely well tolerated by normal tissues and at the same time provide a higher therapeutic index for various tumor models in rodents. The hypothesis of a selective radio-vulnerability of the tumor vasculature versus normal blood vessels by MRT was recently more solidified. SSRT (Synchrotron Stereotactic Radiotherapy) is based on a local drug uptake of high-Z elements in tumors followed by stereotactic irradiation with 80 keV photons to enhance the dose deposition only within the tumor. With SSRT already in its clinical trial stage at the ESRF, most medical physics problems are already solved and the implemented solutions are briefly described, while the medical physics aspects in MRT will be discussed in more detail in this paper.
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Affiliation(s)
- Elke Bräuer-Krisch
- ESRF-The European Synchrotron, 71, Avenue des Martyrs, Grenoble, France.
| | | | - Enver Alagoz
- University of Bergen Department of Physics and Technology, PB 7803 5020, Norway
| | - Stefan Bartzsch
- The Institute of Cancer Research, 15 Cotswold Rd, Sutton SM2 5NG, United Kingdom
| | - Jeff Crosbie
- RMIT University, Melbourne, VIC, 3001, Australia
| | | | - Andrew Dipuglia
- Centre for Medical Radiation Physics, University of Wollongong, Northfields Ave, NSW, Australia
| | - Mattia Donzelli
- ESRF-The European Synchrotron, 71, Avenue des Martyrs, Grenoble, France
| | - Simon Doran
- CRUK Cancer Imaging Centre, Institute of Cancer Research, 15 Cotswold Rd, Sutton Surrey, UK
| | - Pauline Fournier
- ESRF-The European Synchrotron, 71, Avenue des Martyrs, Grenoble, France; Centre for Medical Radiation Physics, University of Wollongong, Northfields Ave, NSW, Australia
| | - John Kalef-Ezra
- Medical Physics Laboratory, University of Ioannina, 451.10, Ioannina, Greece
| | - Angela Kock
- Sintef Minalab, Gaustadalléen 23C, 0373, Oslo, Norway
| | - Michael Lerch
- Centre for Medical Radiation Physics, University of Wollongong, Northfields Ave, NSW, Australia
| | - Ciara McErlean
- CRUK Cancer Imaging Centre, Institute of Cancer Research, 15 Cotswold Rd, Sutton Surrey, UK
| | - Uwe Oelfke
- The Institute of Cancer Research, 15 Cotswold Rd, Sutton SM2 5NG, United Kingdom
| | - Pawel Olko
- Institute of Nuclear Physics PAN, Radzikowskiego 152, 31-342, Krawkow, Poland
| | - Marco Petasecca
- Centre for Medical Radiation Physics, University of Wollongong, Northfields Ave, NSW, Australia
| | - Marco Povoli
- University of Oslo, Department of Physics, 0316, Oslo, Norway
| | - Anatoly Rosenfeld
- Centre for Medical Radiation Physics, University of Wollongong, Northfields Ave, NSW, Australia
| | - Erik A Siegbahn
- Department of Oncolgy-Pathology, Karolinska Institutet, S-177176, Stockholm, Sweden
| | - Dan Sporea
- National Institute for Laser, Plasma and Radiation Physics, Magurele, RO-077125, Romania
| | - Bjarne Stugu
- University of Bergen, Department of Physics and Technology, PB 7803, 5020, Bergen, Norway
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8
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Høye EM, Balling P, Yates ES, Muren LP, Petersen JBB, Skyt PS. Eliminating the dose-rate effect in a radiochromic silicone-based 3D dosimeter. Phys Med Biol 2015; 60:5557-70. [PMID: 26134268 DOI: 10.1088/0031-9155/60/14/5557] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Comprehensive dose verification, such as 3D dosimetry, may be required for safe introduction and use of advanced treatment modalities in radiotherapy. A radiochromic silicone-based 3D dosimetry system has recently been suggested, though its clinical use has so far been limited by a considerable dose-rate dependency of the dose response. In this study we have investigated the dose-rate dependency with respect to the chemical composition of the dosimeter. We found that this dependency was reduced with increasing dye concentration, and the dose response was observed to be identical for dosimeters irradiated with 2 and 6 Gy min(-1) at concentrations of 0.26% (w/w) dye and 1% (w/w) dye solvent. Furthermore, for the optimized dosimeter formulation, no dose-rate effect was observed due to the attenuation of the beam fluence with depth. However, the temporal stability of the dose response decreased with dye concentration; the response was reduced by (62 ± 1)% within approximately 20 h upon irradiation, at the optimal chemical composition and storage at room temperature. In conclusion, this study presents a chemical composition for a dose-rate independent silicone dosimeter which has considerably improved the clinical applicability of such dosimeters, but at the cost of a decreased stability.
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Affiliation(s)
- E M Høye
- Dept of Medical Physics, Aarhus University/Aarhus University Hospital, Aarhus, Denmark
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Juang T, Grant R, Adamovics J, Ibbott G, Oldham M. On the feasibility of comprehensive high-resolution 3D remote dosimetry. Med Phys 2015; 41:071706. [PMID: 24989375 DOI: 10.1118/1.4884018] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
PURPOSE This study investigates the feasibility of remote high-resolution 3D dosimetry with the PRESAGE®/Optical-CT system. In remote dosimetry, dosimeters are shipped out from a central base institution to a remote institution for irradiation, then shipped back to the base institution for subsequent readout and analysis. METHODS Two nominally identical optical-CT scanners for 3D dosimetry were constructed and placed at the base (Duke University) and remote (Radiological Physics Center) institutions. Two formulations of PRESAGE® (SS1, SS2) radiochromic dosimeters were investigated. Higher sensitivity was expected in SS1, which had higher initiator content (0.25% bromotrichloromethane), while greater temporal stability was expected in SS2. Four unirradiated PRESAGE® dosimeters (two per formulation, cylindrical dimensions 11 cm diameter, 8.5-9.5 cm length) were imaged at the base institution, then shipped to the remote institution for planning and irradiation. Each dosimeter was irradiated with the same simple treatment plan: an isocentric 3-field "cross" arrangement of 4 × 4 cm open 6 MV beams configured as parallel opposed laterals with an anterior beam. This simple plan was amenable to accurate and repeatable setup, as well as accurate dose modeling by a commissioned treatment planning system (Pinnacle). After irradiation and subsequent (within 1 h) optical-CT readout at the remote institution, the dosimeters were shipped back to the base institution for remote dosimetry readout 3 days postirradiation. Measured on-site and remote relative 3D dose distributions were registered to the Pinnacle dose calculation, which served as the reference distribution for 3D gamma calculations with passing criteria of 5%/2 mm, 3%/3 mm, and 3%/2 mm with a 10% dose threshold. Gamma passing rates, dose profiles, and color-maps were all used to assess and compare the performance of both PRESAGE® formulations for remote dosimetry. RESULTS The best agreements between the Pinnacle plan and dosimeter readout were observed in PRESAGE® formulation SS2. Under 3%/3 mm 3D gamma passing criteria, passing rates were 91.5% ± 3.6% (SS1) and 97.4% ± 2.2% (SS2) for immediate on-site dosimetry, 96.7% ± 2.4% (SS1) and 97.6% ± 0.6% (SS2) for remote dosimetry. These passing rates are well within TG119 recommendations (88%-90% passing). Under the more stringent criteria of 3%/2 mm, there is a pronounced difference [8.0 percentage points (pp)] between SS1 formulation passing rates for immediate and remote dosimetry while the SS2 formulation maintains both higher passing rates and consistency between immediate and remote results (differences ≤ 1.2 pp) at all metrics. Both PRESAGE® formulations under study maintained high linearity of dose response (R(2) > 0.996) for 1-8 Gy over 14 days with response slope consistency within 4.9% (SS1) and 6.6% (SS2), and a relative dose distribution that remained stable over time was demonstrated in the SS2 dosimeters. CONCLUSIONS Remote 3D dosimetry was shown to be feasible with a PRESAGE® dosimeter formulation (SS2) that exhibited relative temporal stability and high accuracy when read off-site 3 days postirradiation. Characterization of the SS2 dose response demonstrated linearity (R(2) > 0.998) over 14 days and suggests accurate readout over longer periods of time would be possible. This result provides a foundation for future investigations using remote dosimetry to study the accuracy of advanced radiation treatments. Further work is planned to characterize dosimeter reproducibility and dose response over longer periods of time.
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Affiliation(s)
- Titania Juang
- Medical Physics Graduate Program, Duke University Medical Center, Durham, North Carolina 27705 and Department of Radiation Oncology Physics, Duke University Medical Center, Durham, North Carolina 27710
| | - Ryan Grant
- The Graduate School of Biomedical Sciences, University of Texas Health Science Center, Houston, Texas 77030 and Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030
| | - John Adamovics
- Department of Chemistry and Biology, Rider University, Lawrenceville, New Jersey, 08648
| | - Geoffrey Ibbott
- Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030
| | - Mark Oldham
- Department of Radiation Oncology Physics, Duke University Medical Center, Durham, North Carolina 27710
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McCaw TJ, Micka JA, DeWerd LA. Development and characterization of a three-dimensional radiochromic film stack dosimeter for megavoltage photon beam dosimetry. Med Phys 2014; 41:052104. [DOI: 10.1118/1.4871781] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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11
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Skyt PS, Jensen GV, Wahlstedt I, Baltzer Petersen JB, Muren LP, Pedersen JS, Balling P. Investigation of nanoscale structures by small-angle X-ray scattering in a radiochromic dosimeter. RSC Adv 2014. [DOI: 10.1039/c3ra46605a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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12
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Doran SJ, Abdul Rahman AT, Bräuer-Krisch E, Brochard T, Adamovics J, Nisbet A, Bradley D. Establishing the suitability of quantitative optical CT microscopy of PRESAGE® radiochromic dosimeters for the verification of synchrotron microbeam therapy. Phys Med Biol 2013; 58:6279-97. [PMID: 23965895 DOI: 10.1088/0031-9155/58/18/6279] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Previous research on optical computed tomography (CT) microscopy in the context of the synchrotron microbeam has shown the potential of the technique and demonstrated high quality images, but has left two questions unanswered: (i) are the images suitably quantitative for 3D dosimetry? and (ii) what is the impact on the spatial resolution of the system of the limited depth-of-field of the microscope optics? Cuvette and imaging studies are reported here that address these issues. Two sets of cuvettes containing the radiochromic plastic PRESAGE® were irradiated at the ID17 biomedical beamline of the European Synchrotron Radiation facility over the ranges 0-20 and 0-35 Gy and a third set of cuvettes was irradiated over the range 0-20 Gy using a standard medical linac. In parallel, three cylindrical PRESAGE® samples of diameter 9.7 mm were irradiated with test patterns that allowed the quantitative capabilities of the optical CT microscope to be verified, and independent measurements of the imaging modulation transfer function (MTF) to be made via two different methods. Both spectrophotometric analysis and imaging gave a linear dose response, with gradients ranging from 0.036-0.041 cm(-1) Gy(-1) in the three sets of cuvettes and 0.037 (optical CT units) Gy(-1) for the imaging. High-quality, quantitative imaging results were obtained throughout the 3D volume, as illustrated by depth-dose profiles. These profiles are shown to be monoexponential, and the linear attention coefficient of PRESAGE® for the synchrotron-generated x-ray beam is measured to be (0.185 ± 0.02) cm(-1) in excellent agreement with expectations. Low-level (<5%) residual image artefacts are discussed in detail. It was possible to resolve easily slit patterns of width 37 µm (which are smaller than many of the microbeams used on ID-17), but some uncertainty remains as to whether the low values of MTF for the higher spatial frequencies are scanner related or a result of genuine (but non-ideal) dose distributions. We conclude that microscopy images from our scanner do indeed have intensities that are proportional to spectrophotometric optical density and can thus be used as the basis for accurate dosimetry. However, further investigations are necessary before the microscopy images can be used to make the quantitative measures of peak-to-valley ratios for small-diameter microbeams. We suggest various strategies for moving forward and are optimistic about the future potential of this system.
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Affiliation(s)
- Simon J Doran
- Department of Physics, University of Surrey, Guildford, Surrey, UK.
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Gorjiara T, Kacperek A, Kuncic Z, Baldock C, Doran S. Preliminary characterization of PRESAGE®for 3D dosimetry of 62 MeV proton beam. ACTA ACUST UNITED AC 2013. [DOI: 10.1088/1742-6596/444/1/012058] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Skyt PS, Wahlstedt I, Muren LP, Petersen JBB, Balling P. Temperature and temporal dependence of the optical response for a radiochromic dosimeter. Med Phys 2012; 39:7232-6. [DOI: 10.1118/1.4764486] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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